feat(withings): ingest meastype 12 (legacy Thermo temperature) into BODY_TEMPERATURE

First-gen Withings Thermo (WBT01) reports body temperature under
meastype 12. The current-gen Thermo ships meastype 71 (next commit).
Both decode through the same `value * 10^unit` path the client already
applies, and target the `BODY_TEMPERATURE` enum slot we added in v1.4.23
for the Apple Health passthrough.

Adds `src/lib/withings/__tests__/client.test.ts` with a synthetic
`getmeas` payload covering the exponent decode, unknown-meastype skip,
and two-decimal rounding. Re-exports MEASURE_TYPE_MAP so the test can
assert the mapping directly without importing internals.

src/lib/withings/__tests__/client.test.ts

@@ -0,0 +1,89 @@
+import { afterEach, describe, expect, it, vi } from "vitest";
+import { MEASURE_TYPE_MAP, fetchMeasurements } from "../client";
+
+/**
+ * Withings client — meastype mapping + payload-parsing unit tests.
+ *
+ * Each new meastype gets a dedicated case that drives a synthetic
+ * `measure-getmeas` payload through `fetchMeasurements()` and asserts the
+ * mapped row shape. Edge cases (unknown type, missing exponent) live at
+ * the end so a new mapping commit doesn't bloat the diff.
+ */
+
+interface FakeMeasure {
+  type: number;
+  value: number;
+  unit: number;
+}
+
+function fakeGetmeasPayload(measures: FakeMeasure[], date = 1730000000) {
+  return {
+    status: 0,
+    body: {
+      updatetime: "2024-10-27T00:00:00Z",
+      timezone: "Europe/Berlin",
+      measuregrps: [
+        {
+          grpid: 1,
+          attrib: 0,
+          date,
+          created: date,
+          modified: date,
+          measures,
+        },
+      ],
+      more: false,
+      offset: 0,
+    },
+  };
+}
+
+function installFetchMock(payload: unknown) {
+  const fetchMock = vi.fn(async () => ({
+    status: 200,
+    json: async () => payload,
+  }));
+  vi.stubGlobal("fetch", fetchMock);
+  return fetchMock;
+}
+
+afterEach(() => {
+  vi.unstubAllGlobals();
+  vi.restoreAllMocks();
+});
+
+describe("MEASURE_TYPE_MAP", () => {
+  it("maps Withings meastype 12 (legacy Thermo) → BODY_TEMPERATURE", () => {
+    expect(MEASURE_TYPE_MAP[12]).toEqual({ type: "BODY_TEMPERATURE" });
+  });
+});
+
+describe("fetchMeasurements — temperature (meastype 12)", () => {
+  it("decodes the value × 10^unit exponent and emits a BODY_TEMPERATURE row", async () => {
+    // 36.8 °C encoded as Withings exponent shape: value=368, unit=-1.
+    installFetchMock(fakeGetmeasPayload([{ type: 12, value: 368, unit: -1 }]));
+    const out = await fetchMeasurements("token");
+    expect(out).toHaveLength(1);
+    expect(out[0]).toMatchObject({ type: "BODY_TEMPERATURE", value: 36.8 });
+  });
+
+  it("skips an unknown meastype without throwing", async () => {
+    installFetchMock(
+      fakeGetmeasPayload([
+        { type: 12, value: 368, unit: -1 },
+        // 9999 is not in MEASURE_TYPE_MAP → must be ignored.
+        { type: 9999, value: 1, unit: 0 },
+      ]),
+    );
+    const out = await fetchMeasurements("token");
+    expect(out).toHaveLength(1);
+    expect(out[0].type).toBe("BODY_TEMPERATURE");
+  });
+
+  it("rounds to two decimals (Withings sometimes ships fractional exponents)", async () => {
+    // 36.825 → stored as 36.83 once `parseFloat(value.toFixed(2))` runs.
+    installFetchMock(fakeGetmeasPayload([{ type: 12, value: 36825, unit: -3 }]));
+    const out = await fetchMeasurements("token");
+    expect(out[0].value).toBe(36.83);
+  });
+});

src/lib/withings/client.ts

@@ -119,14 +119,18 @@ export async function refreshAccessToken(
   return json.body as WithingsTokenResponse;
 }
 
-// Withings measure type mapping
+// Withings measure type mapping. The single source of truth is
+// `src/lib/withings/mapping.md` — keep both in sync when adding entries.
 // https://developer.withings.com/api-reference#tag/measure/operation/measure-getmeas
-const MEASURE_TYPE_MAP: Record<number, { type: string; factor?: number }> = {
+export const MEASURE_TYPE_MAP: Record<number, { type: string; factor?: number }> = {
   1: { type: "WEIGHT" }, // Weight (kg)
   9: { type: "BLOOD_PRESSURE_DIA" }, // Diastolic BP
   10: { type: "BLOOD_PRESSURE_SYS" }, // Systolic BP
   11: { type: "PULSE" }, // Heart rate
   6: { type: "BODY_FAT" }, // Body fat %
+  // v1.4.25 — first-gen Thermo (WBT01) reports temperature as meastype 12;
+  // current-gen ships meastype 71 instead (see below). Both canonical °C.
+  12: { type: "BODY_TEMPERATURE" },
   77: { type: "TOTAL_BODY_WATER" }, // Hydration / water mass (kg)
   88: { type: "BONE_MASS" }, // Bone mass (kg)
   54: { type: "OXYGEN_SATURATION" }, // SpO2 (% — only ScanWatch / pulse-ox products)